The entropy expression of a Fermi liquid in shielded potential approximation. Application to³He

Abstract

Using the functional representation of the thermodynamical potential, a simple expression for the entropy of a normal Fermi liquid in shielded potential approximation is derived. The result is valid for arbitrary temperatures above a possible phase transition and contains both Fermi (single-particle) and Bose (collective) contributions. It thus represents an improvement over the quasi-particle approximation. — Applying this result to the fluctuation model of liquid³He, we find a Bose contribution of the orderT ³ logT/Θ from spin fluctuations as well as the usual quasi-particle term.